Electrical energy meters are complex devices, which must meet certain American National Standards in order to be compatible with the existing network of electrical distribution equipment. All of these standards regulate design, materials, and use. They also limit the freedom of the designer who must work with the available materials and processes associated with existing electrical energy meter design.
Both the solid state and elector-mechanical residential electrical energy meters of the prior art make generous use of mechanical fasteners such as screws, rivets, eyelets and pins in the assembly of the mechanical package. The large number of different parts used in the typical meter assembly is one of the major cost factors in manufacturing. Using automated assembly equipment has made it possible to manufacture these more complicated meter designs at a reasonable cost only because of the high volume of meters produced.
The majority of electrical energy meters available commercially today utilize thermoset-molding materials for the meter base. Thermoset materials are very hard and brittle, requiring the meter base to have heavy cross sections in order to withstand the impact loads sustained by the meter during shipping and installation. Thermoset material limits the meter design because it is too rigid to support new design features that require resiliency and durability.
It would be desirable to utilize thermoplastic materials in the design of an electrical meter so as to provide flexible yet sturdy construction. In addition to the electrical and thermal properties which are prevalent in thermoses, these flameretardant reinforced, thermoplastic materials also possess excellent mechanical properties. Such mechanical properties enable the design of an electric meter to incorporate snap fit features into a mechanically sound electrical enclosure with high impact strength. It is an object of the present invention to provide a new and unique electrical meter which functions for its intended purpose while significantly reducing the number of parts, simplifying the assembly, and reducing overall product and manufacturing costs. It is a further object of the invention to provide an electrical energy meter with snap fit interlocking parts which eliminates the needs for screws or fasteners.